In known manner in enveloping machines, documents are inserted into envelopes and the envelopes thus filled are then sealed before being loaded into cases of cardboard or plastic.
The number of envelopes capable of being contained in a case varies according to the thickness of those envelopes. It should be noted that the postal services in particular in France have decreed a certain number of rules relating to filling of the cases and identification thereof. Concerning the filling of the cases, these rules are the following:                the play between the envelopes and the inside walls of the case must be sufficient to be able to slide in a hand and thus enable a packet of envelopes to be taken;        the play between the envelopes and the inside walls of the case must not be greater than ten centimeters or so in order to avoid the envelopes being dispersed within the case.The rules of identification decreed by the postal services are the following:        the envelopes contained in a case must be counted and, in certain instances, identified;        the cases must be identified by a standard label.        
In known manner, when the envelopes leave an enveloping machine, they are grasped by an operator who then loads them into a case in order to fill the latter. Given the constraints mentioned above, the loading of the envelopes into cases by an operator proves to be a delicate matter if it is desired to comply with the filling rules. Furthermore, the checks necessary to ensure the compliance with those rules increase the duration of the tasks of the operator and are liable to generate errors.
The present invention therefore aims to mitigate at least one of the drawbacks mentioned above by providing a method of determining the degree of filling of a container with filled envelopes, characterized in that the method comprises the following steps:                dynamically determining the real thickness of each of the filled envelopes of a plurality of filled envelopes before it is loaded into the container,        evaluating the degree of filling of the container on the basis of the real thicknesses of envelopes thus determined.        
The invention thus makes it possible to determine dynamically, i.e. in real time, the degree of filling of a container with envelopes on the basis of the real thicknesses of the envelopes loaded into that container. This method is particularly effective when the envelopes contained in the container do not all have the same thickness. By virtue of the dynamic determination of the thickness of each envelope, the filling of the container can thus be controlled and optimum filling be carried out given the constraints imposed by the postal services. It is thus possible to determine when the container has been filled and thus when the operator must move the latter and put an empty container in its place.
Furthermore, the method makes it possible to know how many envelopes are contained in the container.
Moreover, this manner of determining the degree of filling with envelopes of the container is more reliable than a solution consisting of determining the thickness of the envelopes upstream on the basis of the number of documents of known thicknesses that they contain. More particularly, envelopes of which the thickness has already been calculated by computer means may, for example, never reach the container, which renders the predetermination of its filling imprecise. Moreover, the setting up of calculation algorithms on a production line may sometimes prove to be costly.
According to another aspect, the invention also relates to a method of loading a container with filled envelopes comprising the steps of:                conveying a plurality of filled envelopes from an enveloping machine to a loading station,        loading the filled envelopes into the container, characterized in that the method further comprises the following steps:        dynamically determining the real thickness of each of the filled envelopes before it is loaded into the container,        evaluating the degree of filling of the container on the basis of the real thicknesses of envelopes thus determined.        
The method according to this other aspect has the same advantages as those set forth above for the method of determining the degree of filling of a container with filled envelopes and they will therefore not be repeated here.
According to a feature, the degree of filling of the container is also determined on the basis of the internal dimensions of the container. These items of data may vary and are input into the device for implementing this method by an operator.
According to a feature, the method comprises a step of totaling the sum of the determined real thicknesses for the plurality of filled envelopes.
According to one feature, the selection method comprises the following steps:                comparing the sum of the determined real thicknesses for the plurality of filled envelopes with respect to a predetermined threshold.        and, depending on the result of the comparison, deciding as to the identification of the last envelope of which the thickness has been determined or of the first envelope of the following plurality of envelopes, in order to indicate that the container is full. Thus, when the total of the determined thicknesses reaches the threshold which depends on the internal dimensions of the container, means are provided for identifying the last envelope of which the thickness has been determined or else the next envelope of the following plurality of envelopes and of which the thickness will be determined. By virtue of this identification, the operator who loads the envelopes into the container knows that the container is filled with the loading of that last envelope or that it is already filled without the latter and that he may thus change the container.        
According to a feature, the identification of the envelope is carried out by a marking operation of that envelope. The identification by marking of the envelope enables the operator to visually locate the envelope which will lead to a change in container. This marking may for example take the form of a line of color applied to the edge of the envelope.
According to a feature, dynamically determining the real thickness of a filled envelope is carried out by at least one thickness measurement. By measuring the real thickness of each envelope it is possible to reliably determine the degree of filling of the container. The measurement carried out is, for example, an optical measurement.
According to a feature, to make the thickness measurement, the following steps are carried out:                sending at least one electromagnetic signal from a signal source towards a reference surface and receiving what is referred to as the reference signal reflected by the reference surface,        sending at least one electromagnetic signal towards the reference surface which is placed on the path of a filled envelope and which is brought closer to the signal source on passage of a filled envelope and receiving what is referred to as the measurement signal reflected by the reference surface,        measuring the real thickness of the envelope on the basis of the reference signal and measurement signal that are reflected by the reference surface.        
According to a feature, the method comprises a step during which air is expelled from the envelope in order to determine the real thickness of the latter. By driving out air from the envelope, the dynamically determined thickness is even closer to the reality. Thus a possible volume of air contained in the envelope is taken into account, which a solution calculating the thickness of the envelope on the basis of the number of documents contained therein would not enable.
It will be noted that the invention makes it possible to take into account all the types of folding of documents in the envelopes: folding in two for insertion of documents in an envelope of C5 type, or folding in three for the insertion of the document in an envelope of C6-5 type.
According to a feature, the reference surface placed on the path of the envelopes is both flexible so as to elastically deform on passage of a filled envelope and sufficiently rigid to exert a compressive force on the envelope tending to expel air therefrom. The reference surface is thus used both for the measurements and also to eliminate air contained in the envelope and which would be liable to distort the measurements.
In a complementary manner, the invention relates to a device for determining the degree of filling of a container with filled envelopes, characterized in that the device comprises:                means for dynamically determining the real thickness of each of the filled envelopes of a plurality of filled envelopes before it is loaded into the container,        means for evaluating the degree of filling of the container on the basis of the real thicknesses of envelopes thus determined.        
According to another aspect, the invention also relates to a device for loading a container with filled envelopes comprising:                means for conveying a plurality of filled envelopes from an enveloping machine to a loading station,        means for loading the filled envelopes into the container, characterized in that the device further comprises:        means for dynamically determining the real thickness of each of the filled envelopes before it is loaded into the container,        means for evaluating the degree of filling of the container on the basis of the real thicknesses of envelopes thus determined.        
According to a feature, the means for dynamically determining the real thickness of each of the envelopes comprise thickness measuring means.
According to a feature, the thickness measuring means are optical measuring means.
According to a feature, the optical measuring means are associated with a reference surface.
According to a feature, the thickness measuring means comprise:                means for sending at least one electromagnetic signal from a signal source towards a reference surface and for receiving what is referred to as the reference signal reflected by the reference surface,        means for sending at least one electromagnetic signal towards the reference surface which is placed on the path of a filled envelope and which is brought closer to the signal source on passage of that filled envelope and for receiving what is referred to as the measurement signal reflected by the reference surface,        means for measuring the real thickness of the envelope on the basis of the reference signal and measurement signal that are reflected by the reference surface.        
According to a feature, the reference surface placed on the path of the envelopes is both flexible so as to elastically deform on passage of a filled envelope and sufficiently rigid to exert a compressive force on the envelope tending to expel air therefrom.
Other features and advantages will appear in the following description, which is given solely by way of non-limiting example and made with reference to the accompanying drawings, in which: